Experimental Study of the Boundary-Layer Evolution over a Wind-Turbine Airfoil Using Temperature-Sensitive Paint

Abstract

Knowledge on the boundary-layer transition location at large chord Reynolds numbers is essential to evaluate the performance of airfoils designed for modern wind-turbine rotor blades. In the present work, a temperature-sensitive paint was used to systematically study boundary-layer transition on both sides of a DU 91-W2-250 airfoil. The experiments were performed in the High-Pressure Wind Tunnel Göttingen at chord Reynolds numbers up to 12 million and angles-of-attack from -14° to 20°. The coefficients of airfoil lift, drag, and pitching moment were also obtained after integration of the pressure distributions measured on the surface and in the wake of the wind-tunnel model. The global information obtained via temperature-sensitive paint not only enabled the analysis of the change in the transition location with varying angle-of-attack and chord Reynolds number, but also provided an explanation for the evolution of the aerodynamic coefficients measured at stall and post-stall conditions.